Description
In the Linux kernel, the following vulnerability has been resolved:

sched/psi: fix race between file release and pressure write

A potential race condition exists between pressure write and cgroup file
release regarding the priv member of struct kernfs_open_file, which
triggers the uaf reported in [1].

Consider the following scenario involving execution on two separate CPUs:

CPU0 CPU1
==== ====
vfs_rmdir()
kernfs_iop_rmdir()
cgroup_rmdir()
cgroup_kn_lock_live()
cgroup_destroy_locked()
cgroup_addrm_files()
cgroup_rm_file()
kernfs_remove_by_name()
kernfs_remove_by_name_ns()
vfs_write() __kernfs_remove()
new_sync_write() kernfs_drain()
kernfs_fop_write_iter() kernfs_drain_open_files()
cgroup_file_write() kernfs_release_file()
pressure_write() cgroup_file_release()
ctx = of->priv;
kfree(ctx);
of->priv = NULL;
cgroup_kn_unlock()
cgroup_kn_lock_live()
cgroup_get(cgrp)
cgroup_kn_unlock()
if (ctx->psi.trigger) // here, trigger uaf for ctx, that is of->priv

The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards
the memory deallocation of of->priv performed within cgroup_file_release().
However, the operations involving of->priv executed within pressure_write()
are not entirely covered by the protection of cgroup_mutex. Consequently,
if the code in pressure_write(), specifically the section handling the
ctx variable executes after cgroup_file_release() has completed, a uaf
vulnerability involving of->priv is triggered.

Therefore, the issue can be resolved by extending the scope of the
cgroup_mutex lock within pressure_write() to encompass all code paths
involving of->priv, thereby properly synchronizing the race condition
occurring between cgroup_file_release() and pressure_write().

And, if an live kn lock can be successfully acquired while executing
the pressure write operation, it indicates that the cgroup deletion
process has not yet reached its final stage; consequently, the priv
pointer within open_file cannot be NULL. Therefore, the operation to
retrieve the ctx value must be moved to a point *after* the live kn
lock has been successfully acquired.

In another situation, specifically after entering cgroup_kn_lock_live()
but before acquiring cgroup_mutex, there exists a different class of
race condition:

CPU0: write memory.pressure CPU1: write cgroup.pressure=0
=========================== =============================

kernfs_fop_write_iter()
kernfs_get_active_of(of)
pressure_write()
cgroup_kn_lock_live(memory.pressure)
cgroup_tryget(cgrp)
kernfs_break_active_protection(kn)
... blocks on cgroup_mutex

cgroup_pressure_write()
cgroup_kn_lock_live(cgroup.pressure)
cgroup_file_show(memory.pressure, false)
kernfs_show(false)
kernfs_drain_open_files()
cgroup_file_release(of)
kfree(ctx)
of->priv = NULL
cgroup_kn_unlock()

... acquires cgroup_mutex
ctx = of->priv; // may now be NULL
if (ctx->psi.trigger) // NULL dereference

Consequently, there is a possibility that of->priv is NULL, the pressure
write needs to check for this.

Now that the scope of the cgroup_mutex has been expanded, the original
explicit cgroup_get/put operations are no longer necessary, this is
because acquiring/releasing the live kn lock inherently executes a
cgroup get/put operation.

[1]
BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011
Call Trace:
pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011
cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:43
---truncated---
Published: 2026-06-24
Score: 7.8 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

A race condition exists in the Linux kernel between the PSI (pressure) write operation and the release of a cgroup file. The kernel may free the "priv" member of a struct kernfs_open_file during cgroup removal while a pressure write concurrently accesses it, leading to a use‑after‑free that can trigger a kernel panic. This weakness is classified as CWE‑367 (Race Condition). The primary impact is a denial‑of‑service via a kernel crash.

Affected Systems

All Linux kernel releases that compile with cgroup pressure support (CONFIG_CGROUPS_PSI) are affected until the patch that extends the cgroup_mutex lock to cover all uses of the "priv" pointer in cgroup.c is applied. The fix has been merged in commit 03dc070fa0fc3cb4068693f468ccd5f8a7e58282 and shipped to current stable kernel series.

Risk and Exploitability

The CVSS score of 7.8 indicates high severity, while the EPSS score of < 1 % suggests a low likelihood of exploitation in the wild. The vulnerability is not listed in the CISA KEV catalog. The race involves concurrent operations on the cgroup pressure interface; based on the description, it is inferred that an attacker would need the ability to trigger a PSI write and delete a cgroup directory—capabilities typically available only to a local user with sufficient privileges. The main consequence is a kernel crash that disables the impacted system. No evidence of privilege escalation or data disclosure exists in the available information.

Generated by OpenCVE AI on June 28, 2026 at 15:12 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade the kernel to a version that includes commit 03dc070fa0fc3cb4068693f468ccd5f8a7e58282, which expands the cgroup_mutex lock to prevent the race condition.
  • If an immediate kernel upgrade is not available, disable the cgroup PSI (pressure) interface on the affected system by unmounting or disabling the relevant sysfs nodes or the kernel configuration option CONFIG_CGROUPS_PSI, thereby eliminating the race between pressure writes and cgroup removal.
  • Continuously monitor kernel logs for KASAN or panic messages, and configure automated recovery or alerting to respond promptly if a kernel crash occurs before the patch can be applied.

Generated by OpenCVE AI on June 28, 2026 at 15:12 UTC.

Tracking

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Advisories

No advisories yet.

History

Sun, 28 Jun 2026 12:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362
CWE-416

Sun, 28 Jun 2026 08:00:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

 cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Sat, 27 Jun 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-367
References
Metrics threat_severity

None

 cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Important

Wed, 24 Jun 2026 21:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362
CWE-416

Wed, 24 Jun 2026 17:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: sched/psi: fix race between file release and pressure write A potential race condition exists between pressure write and cgroup file release regarding the priv member of struct kernfs_open_file, which triggers the uaf reported in [1]. Consider the following scenario involving execution on two separate CPUs: CPU0 CPU1 ==== ==== vfs_rmdir() kernfs_iop_rmdir() cgroup_rmdir() cgroup_kn_lock_live() cgroup_destroy_locked() cgroup_addrm_files() cgroup_rm_file() kernfs_remove_by_name() kernfs_remove_by_name_ns() vfs_write() __kernfs_remove() new_sync_write() kernfs_drain() kernfs_fop_write_iter() kernfs_drain_open_files() cgroup_file_write() kernfs_release_file() pressure_write() cgroup_file_release() ctx = of->priv; kfree(ctx); of->priv = NULL; cgroup_kn_unlock() cgroup_kn_lock_live() cgroup_get(cgrp) cgroup_kn_unlock() if (ctx->psi.trigger) // here, trigger uaf for ctx, that is of->priv The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards the memory deallocation of of->priv performed within cgroup_file_release(). However, the operations involving of->priv executed within pressure_write() are not entirely covered by the protection of cgroup_mutex. Consequently, if the code in pressure_write(), specifically the section handling the ctx variable executes after cgroup_file_release() has completed, a uaf vulnerability involving of->priv is triggered. Therefore, the issue can be resolved by extending the scope of the cgroup_mutex lock within pressure_write() to encompass all code paths involving of->priv, thereby properly synchronizing the race condition occurring between cgroup_file_release() and pressure_write(). And, if an live kn lock can be successfully acquired while executing the pressure write operation, it indicates that the cgroup deletion process has not yet reached its final stage; consequently, the priv pointer within open_file cannot be NULL. Therefore, the operation to retrieve the ctx value must be moved to a point *after* the live kn lock has been successfully acquired. In another situation, specifically after entering cgroup_kn_lock_live() but before acquiring cgroup_mutex, there exists a different class of race condition: CPU0: write memory.pressure CPU1: write cgroup.pressure=0 =========================== ============================= kernfs_fop_write_iter() kernfs_get_active_of(of) pressure_write() cgroup_kn_lock_live(memory.pressure) cgroup_tryget(cgrp) kernfs_break_active_protection(kn) ... blocks on cgroup_mutex cgroup_pressure_write() cgroup_kn_lock_live(cgroup.pressure) cgroup_file_show(memory.pressure, false) kernfs_show(false) kernfs_drain_open_files() cgroup_file_release(of) kfree(ctx) of->priv = NULL cgroup_kn_unlock() ... acquires cgroup_mutex ctx = of->priv; // may now be NULL if (ctx->psi.trigger) // NULL dereference Consequently, there is a possibility that of->priv is NULL, the pressure write needs to check for this. Now that the scope of the cgroup_mutex has been expanded, the original explicit cgroup_get/put operations are no longer necessary, this is because acquiring/releasing the live kn lock inherently executes a cgroup get/put operation. [1] BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011 Call Trace: pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:43 ---truncated---
Title sched/psi: fix race between file release and pressure write
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-07-15T00:45:31.101Z

Reserved: 2026-06-09T07:44:35.377Z

Link: CVE-2026-52991

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

Severity : Important

Publid Date: 2026-06-24T00:00:00Z

Links: CVE-2026-52991 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-06-28T15:15:05Z

Weaknesses
  • CWE-367

    Time-of-check Time-of-use (TOCTOU) Race Condition